The purpose of the Clinical Research Center for the Study of Senile Dementia (CRCSD) is to develop innovative studies of patients with Primary Degenerative Dementia (PDD), integrating five different specialty areas. A major theme of the CRCSD is to identify areas of "excess disability" in PDD patients which may be alleviated to improve functional status. The projects are: Biochemical Component (Project #1): This component is attempting to identify cerebrospinal fluid (CSF) biochemical markers for senile dementia which may be useful in the differential diagnosis of early forms of the disease from normals with depression. Particular attention will be directed towards newer peptide markers such as myelin basic protein, glial fibrillary acidic protein and S-100 protein. Electrophysiologic and Brain Imagery Component (Project #2): This component is using measures of electrophysiology and brain imagery to follow the natural course of PDD with the intention of developing better methods of establishing diagnosis and prognosis. Sleep Component (Project #3): This component is studying the relation of disturbed sleep, altered sleep-wake cycles, apneic episodes, daytime sleepiness, and "Sundowning," or nighttime confusion, to excess disability in PDD patients. For the first time a careful assessment of the clinical efficacy of several commonly used medications for "Sundowners" will be undertaken. Medical Component (Project #4): This component is studying the relation of medical illnesses which develop as PDD progresses to excess disability in demented patients. Psychosocial Component (Project #5): This component is studying the course of psychosocial needs of caregivers of PDD patients and will attempt to develop model programs for treating depression in this group. One hundred anad fifty patients with PDD and 108 controls will be followed for at least two years and evaluated on core cognitive/behavioral measures using specialized testing by each Project. Each Project will test important hypotheses within its specialty; however hypotheses bridging specialized areas will also be tested, e.g., whether spinal fluid markers relate to sleep disorders.